The present invention is an improvement over the envelope and sheet feeding apparatus disclosed in U.S. Pat. No. 3,934,868. As disclosed therein, the feeding apparatus includes three widely spaced suction cups supported on individual arms movable between an initially lowered position and a raised position where the suction planes of the suction cups are parallel to and engage the bottom exposed surface of the bottommost sheet in a stack of the same held in a top loadable stacking frame, so that the operation of the apparatus does not have to be interrupted when the supply of sheets is to be replenished. The stack of sheets preferably rests on a slightly forwardly inclined support tray which terminates short of the lower front end of the stack to leave an opening running the entire width of the stack to expose thereat the bottom sheet in the stack for engagement by one or more of the suction cups. The front end of the stack rests on a rigid support ledge so that when the bottommost sheet is pulled from the stack by the lowering of the suction cups, the weight of the stack above the same will tend to maintain this next sheet within the stacking frame. The suction applied to the suction cups is released in the lowermost position thereof where the sheet is applied to a feed or drive roller which directs the sheet to other sheet feeding apparatus.
The width of the front support ledge for the stack of sheets described was also found to be of importance. It was found that the width of the support ledge for rigid sheets of material is desirably much narrower than when the ledge supports very flexible sheet material. Since sheet feeding machines are generally sold for use with a variety of types of sheet material, a width for the support ledge is selected which is a compromise between the ideal widths for rigid and flexible sheet materials, with the result that sometimes the weight of the stack of sheets will cause very flexible sheet material undesirably to slip below a ledge which is undesirably narrow, or will undesirably interfere with the easy removal of a bottommost rigid sheet so that the suction cups will slip from the sheet during their downward movement from the stack when the ledge is undesirably wide. It is, accordingly, an object of the invention to provide sheet feeding apparatus with an improved support ledge construction which avoids these problems.